Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.82	12.537%	$161.8507	$161.85	$161.85	$161.90
Purchase #2	$36.94	10.726%	$40.9022	$40.90	$40.90	$40.90
Purchase #3	$73.88	4.271%	$77.0354	$77.04	$77.05	$77.00
Purchase #4	$84.26	6.688%	$89.8953	$89.90	$89.90	$89.90
Purchase #5	$141.57	13.299%	$160.3974	$160.40	$160.40	$160.40
Purchase #6	$206.77	12.103%	$231.7954	$231.80	$231.80	$231.80
Purchase #7	$6.50	5.125%	$6.8331	$6.83	$6.85	$6.80
7 purchase totals =	$693.74		$768.7095	$768.72	$768.75	$768.70